CN108746960A - A kind of new method that the friction stir welding keyhole based on resistance plug welding principle is filled up - Google Patents

Abstract

The invention discloses a kind of friction stir welding keyholes based on resistance plug welding principle to fill up new method, implementation process is, stopper is preset in keyhole to be filled up, apply electric current and pressure to stopper and keyhole by the top electrode of resistance welder, lower electrode, the contact resistance moment between stopper and keyhole is promoted to generate heat, fusing or softening faying face metal, finally under the action of forging force, stopper generates metallurgical binding with keyhole circumference and bottom, completes keyhole and fills up；The principle of this method is similar to resistance plug welding, and the bulk resistor of stopper and keyhole serves as heat source；The advantages of this method is without external heat source, easy to operate, efficient, easy to automate；This method can be used for agitating friction weldering and friction stir spot welding postwelding keyhole is filled up, and be particularly suitable for the occasion that the keyholes such as circular weld can not be drawn, and can effectively improve stir friction welding seam aesthetics and corrosion resistance.

Description

A kind of new method that the friction stir welding keyhole based on resistance plug welding principle is filled up

Technical field

The present invention relates to one kind being applied to the reparation of agitating friction weldering broken needle weld seam, agitating friction weldering and friction stir spot welding weldering The new method that keyhole is filled up afterwards.

Background technology

Agitating friction weldering (Friction Stir Welding, abbreviation FSW) is Britain's institute of welding (The Welding Institute, abbreviation TWI) in the patent welding technique of invention in 1991.Since heat input is opposite during agitating friction weldering Smaller in fusion process, the metal of joint area does not undergo high temperature melting, is a kind of solid State Welding process, keeps female in the alloy The metallurgical performance of material can use melting welding to have bad anti-with welding metal based composites, dissimilar material, rapidly solidified material etc. The material answered.Currently, agitating friction welding technology is obtained in industry manufacture fields such as Aeronautics and Astronautics, automobile, shipbuilding, motor-car, high ferros It is widely applied.

Technology is eliminated or fills up for the keyhole of stir friction welding seam tail portion, the method that domestic and foreign scholars propose mainly is wrapped It includes：Draw welding, friction plug welding method, melting welding enthesis, riveting and the backfill formula weldering using the welding of telescopic stirring-head Connection etc..Above-mentioned various methods have its superiority and limitation.Extraction method refers to that stirring-head is kept welded condition, gradually It removes workpiece and retreats to end tab, the welding method being finally retained in keyhole on end tab.Its limitation is to can be used only in opening Property weld seam, and for circular weld tail portion keyhole, it is difficult to be removed using extraction method；Riveting, being will be special using riveting process Rivet riveting enters in keyhole, plays the role of filling up keyhole；Melting welding enthesis, using non-melt pole or consumable electrode noble gas protective The weld metal around metal and keyhole is filled in the method for weldering, fusing, forms melting welding head, the final effect realized keyhole and filled up Fruit.But since agitating friction weldering welding object is mainly aluminium alloy, some aluminium alloys easily generate fire check when dissolving weldering, Then whole weld strength is caused to decline, therefore, the method for fusion welding repair keyhole has its innings of limitation；Friction plug welding method utilizes The principle of spin friction weldering, fills up a kind of method of keyhole.Such method, is initially invented in nineteen ninety-five by TWI, and recommends U.S. The Lockheed Martin Corporation (Lockheed Martin Space Systems Company) of state, Du B., Luan Guohong, Ji Ya Beautiful et al. result of study shows that friction plug welding method fills up the technology of keyhole to technological parameter, plug welds design, stopper and keyhole It is more demanding to moderate etc., it is difficult to engineering promote；Welding is backfilled, mixing needle extension type stirring-head used is by state of the U.S. Aeronautics and Space Administration of family (NASA) designs and makes for the first time, and has many scholars to study such method (or similar) in succession and welded The institutional framework and mechanical property of head.Although backfill formula welding gradually withdraws mixing needle in weld seam tail end, can be quickly and efficiently Keyhole is filled up, but its stirring-head is complicated, processing difficulties, is hidden in pressure ring (clamping ring) and telescopic shaft shoulder (sleeve) the weldment metal between and between telescopic shaft shoulder and scalable mixing needle (probe) is difficult to remove, and keyhole is filled out Loose class defect is also easy to produce at benefit., be not suitable for the industrial application of weldment batch production.

In view of the above-mentioned research situation for filling up technology to keyhole both at home and abroad, become in conjunction with current energy saving, efficient industrial development Gesture, the present invention proposes a kind of new method that the friction stir welding keyhole based on plug welding principle is filled up, i.e., preset one in keyhole Root stopper applies electrode pressure and welding current, in the collective effect of electrode pressure and welding current using plug welding machine to stopper Under, promote the contact resistance moment between stopper and keyhole to generate heat, fusing (or softening) faying face metal, finally in forging force Under effect, stopper generates metallurgical binding with keyhole circumference and bottom, is filled up to complete keyhole.

Invention content

The purpose of the present invention is to provide a kind of methods that the friction stir welding keyhole based on plug welding principle is filled up, in keyhole An interior preset stopper applies electrode pressure and welding current, in electrode pressure and welding current using resistance welder to stopper Collective effect under, promote the contact resistance moment between stopper and keyhole to generate heat, fusing or softening faying face metal, finally exist Under the action of forging force, stopper generates metallurgical binding with keyhole circumference and bottom, is filled up to complete keyhole.

It is as follows：

(1) start-up resistor welding machine sets fill process；

(2) according to keyhole depth, prefabricated stopper；

(3) using mechanically or chemically cleaning keyhole and the oxidation film of stopper contact surface and greasy dirt etc.；

(4) stopper is positioned in keyhole naturally；

(5) keyhole for being built-in with stopper is positioned over to the upper end of lower electrode, pays attention to adjusting keyhole central axes and lower electricity Pole central axes essentially coincide；

(6) start fill process cycle；

(7) fill process after circulation terminates, lift automatically by top electrode, between upper and lower electrode take out fill up after workpiece；

(8) filling is completed, resistance welder is shut down.

A preset stopper, the volume of the stopper it need to be slightly larger than keyhole volume in keyhole before filling up；Its shape with wait for Fill out that keyhole depth is related, the shallower keyhole of depth can use pole as stopper, the deeper keyhole of depth, must with keyhole shape Similar bar is as stopper；In addition, stopper material should to keyhole material identical or similar, to guarantee in stopper and keyhole Metallurgical binding is generated at faying face.

Device therefor is electric resistance welding equipment, and fill process is low current, prolonged soft specification；Filling is divided into soft Change, automatic centering, cooperation stage, exhaust, metallurgical stages, forging and stamping, cooling stage；It is undertaken in filling and transmits pressure and electricity The upper and lower electrode structure for flowing role is similar but different, and top electrode end diameter is less than lower electrode tip diameter.

As being further improved for this programme, regardless of keyhole depth, stopper structure size need not be consistent with keyhole, Only need to be cylinder；Stopper cost of manufacture will be greatly reduced in this improvement.

The technique effect of the present invention：This method has easy to operate, it is easy to accomplish and mechanization and automation, productivity is high, And noiseless and pernicious gas can be compiled on assembly line, metallurgical process together in mass production with other manufacturing processes Simply, the low equal outstanding advantages of welding cost.It is with the obvious advantage, and be expected to be applied in domestic agitating friction weldering actual production, to stir Popularization of the friction welding technology in China is mixed to contribute with development.

Description of the drawings

Fig. 1 is keyhole schematic diagram.In figure：1-keyhole, 2-stoppers

Fig. 2 is stopper schematic diagram.In figure：2- stoppers

Fig. 3 is electrode tip outline drawing.In figure：3-top electrodes, 4-lower electrodes

Fig. 4 is keyhole filling schematic diagram.

Fig. 5 is keyhole and stopper geometric dimension schematic diagram in embodiment 1.

Fig. 6 is that keyhole fills up connector photomacrograph in embodiment 1.In figure：61-pressings (61) 62-fusion zone of area (62) (63) 64-plastically deforming area of 63-fusion area (64).

Fig. 7 is that keyhole fills up micrograph in embodiment 1.In figure：7-a-stopper and keyhole bottom fusion welding area.

7-b-stopper circumference and keyhole inner wall pressing Diffusion Welding area.

7-c-stopper top plastically deforming area.

Fusion zone in the middle part of 7-d-stopper.

Fig. 8 is that keyhole fills up hardness cloud atlas in embodiment 1.

Specific implementation mode

A method of the friction stir welding keyhole based on plug welding principle is filled up, and its step are as follows：

(1) it assembles：It will be in stopper (2) merging keyhole (1)；

(2) to be welded：The stopper assembled and keyhole are placed between top electrode (3) and lower electrode (4), keyhole, stopper are made And upper/lower electrode three's almost coaxial；

(3) it fills up：Program is filled up in startup；

(4) pickup：Workpiece after keyhole is filled up takes out between upper and lower electrode.

Embodiment 1

1.1 test material

It is duralumin, hard alumin ium alloy LY12, thickness 3.0mm to test institute's wlding material, and overlap joint assembly is prepared as shown in Figure 5 in the middle part of test piece Keyhole, keyhole depth 5.5mm, upper diameter 10.0mm, base diameter 4mm；Stopper shape is as shown in Fig. 2, smaller for taper In the frustum cone structure of keyhole, top diameter 10.0mm, base diameter 4.0mm, length 7.0mm；Keyhole inner wall has mixing needle screw thread Tooth mark helps to improve the contact resistance of stopper and keyhole, disperses the current line for flowing through the two.

1.2 macroscopic view formings and principle analysis

According to soldering theory and crystallography, herein by the surrounding bonding pad in connector cross section, bottom bonding pad and stopper institute It is specifically defined as fusion area (63) in region and sees that mark 63 in Fig. 6, pressing area (61) are shown in mark 61 in Fig. 6, plastically deforming area (64) see that mark 62 in Fig. 6 is seen in mark 64 and fusion zone (62) in Fig. 6.

Fusion area (63) refers to the region that stopper bottom surface is connect with keyhole bottom, which forms the main original of fusing connection Because having at following 2 points：First, since electrode pressure is perpendicular to stopper bottom surface and keyhole bottom surface, fusion area (63) pressure is the most Fully, contact surface is in good condition, contact resistance is minimum；Second, due between fusion area (63) are in upper and lower electrode charge it is most short In access, therefore most of welding current must preferentially flow through the region；It is theoretical in conjunction with electric resistance welding in view of above-mentioned 2 reasons, The principle that stopper bottom surface forms fusing connection with keyhole bottom is set up.It is smaller that fusion area (63) is only limitted to keyhole bottom, area, leads to Electricity fills up initial stage, that is, fusing connection, contact resistance pop-off occurs, and stopper combined with keyhole bottom metallurgical, composition electric current and The better channels of heat；By adjusting technological parameter and stopper shape, accurately controls fusion area (63) and form the time, be based on electricity Thermal resistance carries out the key that keyhole is filled up.

Pressing area (61) refers to the region that stopper periphery is connect with keyhole side, and the catenation principle in the region belongs to diffusion Weld scope.Stopper is under the collective effect of resistance heat and electrode pressure cross component force, the atom phase counterdiffusion of contact surface, most end form It is combined between atom.Since the material of stopper is aluminium alloy, bulk resistor is much smaller than the contact resistance of the faying face, therefore flows through The electric current of the contact surface is few, promotes the energy of atoms permeating to mostly come from the heat of stopper bulk resistor generation, followed by fills in The interface energy that stick and keyhole generate in process.The efficiency of diffusion welding (DW) is far below electric resistance welding, with regard to " being fully connected the moment " Speech, pressing area (61) lag far behind fusion area (63)；The time difference between the two is conducive to be expelled from the sky between stopper and keyhole Gas prevents to generate stomata and trapped oxide in connector.

Plastically deforming area (64) refers to stopper under the action of electrode pressure and resistance heat, generates the region of plastic deformation, It is filled in the range of fusion area (63) and pressing area (61) encirclement, upper part is by top electrode tail end plugs.Plastically deforming area (64) contribute to stopper to be full of keyhole, and reduce requirement of the fill process to stopper shape, stopper-keyhole to moderate.

Fusion zone (62) typically occurs in the middle part of stopper, is plastically deformed the position of area (64) package.The position is away from upper and lower Relatively far away from, when welding current flows through stopper, bulk resistor generates rapidly big calorimetric to electrode, cannot be scattered and disappeared in time by electrode, The stopper middle portion temperature is caused drastically to increase, temperature is more than the region of fusing point, and melting phenomenon will occur for stopper.Ensureing to press Under conditions of area (61) institute calorific requirement is enough, by adjusting technological parameter and stopper shape, reduces, even prevents fusion zone (62) It generates, helps to improve keyhole and fill up quality.

1.3 microstructures and Analysis on Mechanism

Microstructure be analyze and determine connector forming process, formation mechenism Main Basiss, be also that evaluation keyhole fills up matter The leading indicator of amount.

As shown in Fig. 7-a, fusion area is stopper and keyhole bottom superficial contact surface fusion welding area, the region liquid metal Thickness is thin, and fusing time is short, crystallization rate is fast, and grain form is based on tiny equiax crystal and column crystal, 8 microns of left sides of diameter The right side, 18 microns of the latter's cross-sectional diameter.Fusion area top stopper plastically deforming area crystal grain is tilted, keyhole side section Grain form inherits the region column crystal gene, sees in figure shown in arrow, and grain growth direction is from stopper to keyhole；It is tiny etc. Axialite grain is formed using keyhole bottom recrystal grain as forming core structure cell to stopper directional solidification.Stopper original grain metamorphosis is special Sign shows in filling that keyhole bottom melts layer thickness and is more than stopper end, the reason is that polishing is passed through in stopper end, Surface roughness is less than keyhole bottom, and keyhole side current density is unevenly distributed, and the heating effect of contact resistance heat is apparent, temperature liter It is high rapid, cause fusion penetration to be more than stopper.Keyhole bottom finish is improved, its contact resistance with stopper is reduced, delays fusion area (63) time is formed, pressing area's temperature is helped to improve, is created favorable conditions to ensure that keyhole integrally fills up quality.

As shown in Fig. 7-b, pressing area belongs to Diffusion Welding area, and there are notable difference, self-diffusions for crystallite dimension and crystal grain orientation It is the principal mode of metallic atom migration.Stopper process and extrusion process is filled up, increased surface energy is that metallic atom expands It dissipates and provides driving force.When crystal boundary moves, metallic atom is migrated by the little crystal grain of stopper side to keyhole side big crystal grain, is occurred big brilliant Grain annexes little crystal grain phenomenon.After the completion of keyhole is filled up, stopper side plastically deforming area column crystal has crimp phenomenon, keyhole side big Crystal grain showed increased, in addition to partly belonging to recrystal grain and growing up and to form isometric big crystal grain, close to the column big crystal grain of contact surface Mainly annex stopper little crystal grain to grow up to be formed.(ensure that stopper has foot under conditions of ensureing that electrode pressure effectively transmits Enough hardness), extend pressing area's high-temperature residence time, helps to increase thickness of diffusion layer and uniformity, then ensure that keyhole is filled up General effect.

As shown in Fig. 7-c, stopper top plastically deforming area, under electrode pressure effect, former rolled fiber tissue occurs " geometry softening " phenomenon of deformation is bent, to bend inflection point line as boundary, based on reply phenomenon, reply is arranged at lower part on boundary line top With recrystallization phenomenon, region bigger is recrystallized, but its crystal grain is mostly tiny equiax crystal, is illustrated as stopper is away from top electrode central part The distance of position gradually increases, and under bulk resistor heat effect, temperature, which rises, gradually to be increased, but the principle of such complementing method determines, It is of short duration in high-temperature residence time, and crystal grain not grow up by the sufficient time.According to metal plastic deformation and recrystallization principle, project Select drawing aluminium bar as stopper raw material, selection is beneficial to stopper along plate where keyhole in all plates of keyhole to be filled up The calendering deformation of face direction delays Recovery and recrystallization phenomenon to generate, and keeps stopper mechanical property.

Shown in Fig. 7-d, fusion zone microstructure, mainly equiaxed dendrite.Stopper Body resistance heating, and largely accumulated at middle part It is poly-, there is liquid phase solidified structure, has no stopper original structure.Since stopper middle part is farthest away from upper and lower electrode distance, radiates most Difference, when its circumference and bottom reach with keyhole metallurgical binding temperature condition, liquid phase or solid-liquid coexistence must occur in middle part Domain.To prevent liquid metal in crystallization process, solidification cracking is generated under the action of crystal grain shrinkage stress, need to be applied to electrode Sufficiently large pressure.

In conclusion when filling up friction stir welding keyhole using press welding method, according to keyhole shape, size, it should integrate and examine Consider size of current and conduction time, pressure size and time adjustment, stopper size and crystal grain position to etc. technological parameters.

1.4 hardness nephanalysis

Test point spacing 0.5mm, Fig. 8 connector microhardness distribution cloud atlas load 0.2kgf, protects lotus 10s.It is hard around keyhole It spends uniform, relatively low, has no apparent gradient, hardness number illustrates that keyhole filling is not organized it and property between 40HV-50HV It can generate and significantly affect.Keyhole and stopper fusion area hardness gradient are apparent, and from stopper side, 90HV is gradually decrease to keyhole side 50HV, fusion area (63) metallurgical reaction depth is about 0.5mm.Fusion zone hardness is minimum (60-70HV) in the middle part of stopper, and part is low To 60HV hereinafter, from-inner-to-outer gradually rises, gradient distribution is apparent；Illustrate stopper in filling, middle part liquid phase depth is about It is about 4mm for 1mm, width, for solid-liquid coexistence package with outside liquid phase, thickness about 0.5mm, width cross over stopper mid diameter model It encloses.Stopper plastically deforming area original intergranular is replied serious, and hardness declines notable, leads to this area's hardness is high and low to be alternately distributed, although always Body hardness is higher than other regions, and mean value is in 80HV or more, but when being parallel to board direction pulling force effect, between surface microstructure Hardness lower region will be that formation of crack plays position.In conjunction with Microstructure of Joint form, comprehensive analysis hardness cloud charts, it is known that： Change stopper crystal grain position to, improve upper/lower electrode cooling rate, contribute to that hardness is uniformly distributed, reduces soft area range, reach and change The effect of kind connector overall mechanical properties.

Embodiment 2

Weldment (duralumin, hard alumin ium alloy 5083-O, plate thickness 1.5mm+1.5mm) with keyhole is packed into plug welding fixture (5), is made Keyhole center line-up jig center clamps weldment.Then pre-processed stopper (2) is packed into keyhole (1), the folder that will be installed Tool (5) is inserted in the lower electrode (4) of plug welding machine, and weldment is made to be come into full contact with lower electrode (4).Plug welding machine is opened, waits for that welding machine preheating is filled After point, the size and pressure time and welding current (size and pressure time), electrode fall time that adjust electrode pressure are 35 cycles, preload pressure 3.4KN, squeeze time are 20 cycles, and the weldering pressure time is 25 cycles, and pre- thermocurrent is 20KA, preheating current time are 10 cycles, and welding pressure 2KN, welding current 55KA, the welding current time was 10 week Wave, pressure are held time as 22 cycles, forge pressure 3.4KN, and forge time is 1 cycle, and (a cycle time is 0.02s).After the welding button for pressing plug welding machine, the cylinder of plug welding machine drives top electrode (3) to move downward, top electrode (3) contact To after stopper (2), top electrode (3) pushes stopper (2), is pressed into the keyhole (1) for being placed in lower electrode and applies welding current, promotees The contact resistance moment between stopper (2) and keyhole (1) is set to generate heat, fusing (or softening) faying face metal.Face metal to be combined Fully after fusing (or softening), plug welding machine automatically cuts off welding current according to the time is preset, and discharges electrode pressure and raises Top electrode (3).By fixture (5) Panasonic with weldment, and removes and completed the weldment that keyhole is filled up.

Claims (3)

1. a kind of new method that the friction stir welding keyhole based on plug welding principle is filled up, which is characterized in that with resistance welder be fill out Equipment is mended, required electric current is filled up and pressure comes from the top electrode of resistance welder, lower electrode, utilize connecing between stopper and keyhole The resistance heat that resistance generates of getting an electric shock melts for heat source or softens joint surface metal, and finally applying forging force makes stopper and keyhole inner wall Metallurgical binding is generated, achievees the effect that fill up keyhole, a preset stopper, the volume of the stopper need to be omited in keyhole before filling up More than keyhole volume；Stopper shape is related with keyhole depth to be filled out, and the shallower keyhole of depth can use pole as stopper, depth Deeper keyhole must use the bar consistent with keyhole shape as stopper；In addition, stopper material should be with keyhole material identical or phase Seemingly, to guarantee to generate metallurgical binding at stopper and keyhole faying face.

2. the new method that the friction stir welding keyhole according to claim 1 based on plug welding principle is filled up, which is characterized in that Preset stopper in keyhole realizes the energy source of metallurgical binding using resistance heat as stopper and keyhole；Use the electric resistance welding Machine is filling equipment, is as follows：

(1) start-up resistor welding machine sets fill process；

(2) according to keyhole depth, prefabricated stopper；

(3) using the oxidation film and greasy dirt for mechanically or chemically clearing up keyhole and stopper contact surface；

(4) stopper is positioned in keyhole naturally；

(5) keyhole for being built-in with stopper is positioned over to the upper end of lower electrode, adjustment keyhole central axes and lower electrode central axes To coincidence；

(6) start fill process cycle；

(7) fill process after circulation terminates, lift automatically by top electrode, between upper and lower electrode take out fill up after workpiece；

(8) filling is completed, resistance welder is shut down.

3. the new method that the friction stir welding keyhole according to claim 1 based on plug welding principle is filled up, which is characterized in that The shape of the stopper is the axial symmetry revolving structures such as cylindrical or truncated cone-shaped, and it is straight that top electrode end diameter is less than lower electrode tip Diameter.